The invention relates to a device for measuring the temperature of a transmission oil.
In a vehicle transmission, for different reasons, it is required to measure the temperature of the lubricant used in the transmission and to supply different control devices. The temperature becomes necessary especially for diagnosis problems and for calculation of maintenance intervals. When a preset temperature threshold is exceeded, a warning is issued to the user of the vehicle.
Former systems have a measurement element directly mounted in the oil sump of the transmission. For example, a separate electronic system is needed for the evaluation of the signal. Further required is a not inconsiderable disbursement in cabling which is costly and exerts negative influences upon the reliability.
The problem on which the invention is based is to indicate a device for measuring the transmission oil temperature which offers an increased reliability at low cost.
The problem is solved by a device having the features of claim 1 or x (sic). Developments are object of sub-claims.
The invention proposes a device for measuring the temperature of the oil in a housing of a transmission having a temperature sensor which can come into contact with the oil in the transmission. The temperature sensor is here placed outside the oil sump in the transmission housing. In an advantageous development, the temperature sensor comes into contact with the oil during operation of the transmission by wetting with oil spray. To that end, in an advantageous development, the oil spray is whirled up by rotating elements in the transmission, the rotating elements being gear wheels of the transmission. In one other advantageous development, the temperature sensor is situated in the immediate proximity of a speed sensor with rotary meter disk so that the spray oil is sprayed on the temperature sensor by the meter disk.
Another advantageous development shows a temperature sensor which, during operation of the transmission, comes into contact with the oil via a lubricant circuit. In an advantageous development, the temperature sensor can be disposed in the pressure area of the lubricant circuit directly in parts of the transmission which contains the electronics and the shift actuation system.
One other advantageous development shows the temperature sensor integrated in another sensor, especially in a speed sensor.
In another advantageous development of the invention, the signals of a sensor of the transmission, which does not primarily serve for temperature detection, can be evaluated in an electronic control system for detection of the temperature. In an advantageous development of this, the inner resistance of a speed sensor can be detected and the change of temperature of the transmission oil can be evaluated in an electronic control system by the change of the inner resistance.